Not sure why you picked D300 to compare. Why not D70? I've seen incredible amount of amazing landscape work shot with it when it first came out... 8 years ago or so?

I've got rid of my D300 long time ago so I can't speak to its capabilities, however, when I compared a landscape shot (just a bunch of trees in the back yard) from D800 to D700 - they were not anywhere close to one another. The level of details D800 resolved was mind blowing - it was showing tiniest leaves which were complete blur on D700....